Expected ALICE performance on open heavy flavour and quarkonia

HAL Id: in2p3-00157669

http://hal.in2p3.fr/in2p3-00157669

Submitted on 26 Jun 2007

HAL is a multi-disciplinary open access

archive for the deposit and dissemination of

sci-entific research documents, whether they are

pub-lished or not. The documents may come from

teaching and research institutions in France or

L’archive ouverte pluridisciplinaire HAL, est

destinée au dépôt et à la diffusion de documents

scientifiques de niveau recherche, publiés ou non,

émanant des établissements d’enseignement et de

recherche français ou étrangers, des laboratoires

and quarkonia

R. Guernane

To cite this version:

avour and quarkonia

Ra hid Guernane

∗

for the ALICE Collaboration

Laboratoirede Physique Corpus ulaire de Clermont-Ferrand, CNRS-IN2P3

24,AvenuedesLandais, 63177AUBIÈRECEDEX FRANCE

E-mail: guernane lermont.in2p3.fr

Heavyavourspromisetobevaluableprobestoelu idatethenatureofthehotanddense

matterformed inheavyion ollisions. Heavyquarks,produ ed ininitial hards attering

pro esses,areexpe tedtosuerin-mediumenergyloss. Asforheavyquarkoniumstates,

regeneration pro esses might ounterbalan e olour-s reening ee ts. ALICE through

a omprehensive heavy avour program, will address these open questions beneting

from unique LHC onditions: unpre edentedlarge produ tion ross se tions andinitial

temperaturesexpe tedtobehighenoughtodissolvebottomonia. Inthistalk,wereviewa

sele tionofsigni ativeheavyavourmeasurementsplannedtobeperformedbyALICE.

High-

p

t

physi satLHC workshop Universityof Jyväskylä,Finland

Mar h, 23-272007

∗

1. INTRODUCTION

Heavy avour produ tion at hadron olliders is, for many years now, a very a tive

eld of resear h providing valuable insights into Quantum ChromoDynami s(QCD)

phe-nomenology [1 , 2℄. In nu leon-nu leon (NN) ollisions, heavy quark-antiquark pair

pro-du tion should be well des ribed with the parton-model approa h sin e the heavy quark

mass an be onsidered su iently large with respe t to the fundamental QCD s ale [3℄.

Perturbative QCD ross-se tions for heavy avour produ tion have been omputed up to

Next-to-Leading-Order (NLO) a ura y [4℄, even if quantitatively large un ertainties

re-main, typi ally a fa tor

2 ÷ 3

at LHC energies [2℄. ALICE ben hmark ross-se tions for heavy avour produ tion at the LHC omputed using a Fixed-Order NLO massive

al u-lationfrom Manganoet al. [4℄arepresentedinTab.1[2 , 5,6 ℄.

Table 1: ALICEben hmarktotal ross-se tionsforheavyquark(

σ

Q ¯

Q

)andquarkoniumin lusive leptonpair(

σ

µ

+

µ

₋

)produ tioninPb-Pbandp-p ollisions.

σ

µ

+

µ

₋

arepredi tedfromtheColour Evaporation Model [6, 8℄. For Pb-Pb, parton distribution nu lear modi ationfrom the EKS98

parametrisation[7℄isin ludedandbinarys alingfromnu leon-nu leon ross-se tionsisassumed.

Colliding system Pb-Pb p-p

√

_s

NN

(TeV) 5.5 14

Flavour

c¯

c

b¯b

c¯

c

b¯b

Centrality entr. (5%) min.-bias

σ

Q ¯

Q

(b) 45.0 1.79 0.0112

5.1 × 10

−4

N

Q ¯

Q

per ollision 115 4.56 0.16 0.0072 State J/

ψ

ψ

′

_Υ

_Υ

′

_Υ

′′

J/

ψ

ψ

′

_Υ

_Υ

′

_Υ

′′

Centrality min.-bias min.-bias

σ

µ

+

_µ

−

(

µ

b) 48930 879 420 109 61 3.18 0.0057 0.028 0.0069 0.0041

Inheavy-ion ollisions,openheavyavourprodu tionis onsideredtobeaninteresting

probe for studying properties of the dense QCD medium [9 , 10 ℄. Heavy quarks, on e

produ ed at the initial stage of the rea tion in hard parton intera tions, are expe ted to

res atter and loseenergy traversingthesurroundingmatter, testing this way theexpe ted

massdependen eofpartonenergyloss[11℄. Inparti ular,itwillbeimportantinALICEto

measureheavyavouredparti letransversemomentumdistributionswhi hareexpe tedto

be remarkablysensitive todierent ee ts[12 ℄. Thelow-

p

t

(

< 6 GeV/c

attheLHC)region is expe ted to be sensitive to various non-perturbative ee ts (su h as gluon shadowing,

Colour-Glass-Condensatestate[14 ℄,ow,quark oales en e[13 ℄...);whilethehigh-

p

t

region is expe ted to be essentially sensitive to jet quen hing [15 ℄, namely an attenuation (or

slowing down) ofheavy quarkjetsafter propagationthrough thedensemedium.

In a de onned medium, quarkonium disso iation due to olour s reening has been

predi ted [16℄ with disso iation temperatures expe ted to be ordered a ording to the

hi-erar hy ofquarkonium sizes. Consequently, lesstightly bound ex itedstates arepredi ted

to dissolve at lower temperature than their orresponding smaller ground states, leading

resonan es ould survive even inthe de onned Quark-Gluon Plasma (QGP): J/

ψ

and

η

c

ouldsurviveuptotemperatures

T ≃ 1.6 T

c

andmeltsomewherebetween

1.6 T

c

and

1.9 T

c

[18 ℄ while

η

b

state ould survive up to

T = 2.3 T

c

[19℄. At the LHC, with the in rease inavailable entre-of-mass energy,suitable onditions will beprovided for detailed studies

to be performed espe iallyinthebottomonium se tor: produ tion ross-se tions arelarge

(see Tab. 1) both for p-p and Pb-Pb ollisions and initial temperatures are expe ted to

be highenough (

T

0

≃ 1 GeV

fora gluon-dominated plasmaformation expe ted for entral Pb-Pb at the LHC [21, 22℄) to melt bottomonium states. However, given the large

num-ber of un orrelated

Q ¯

Q

pairs initially produ ed at LHC energies ( f. Tab. 1), this simple step-like suppressionpattern ouldbe ounterbalan edbytheoutbreakof oales en e (e.g.

re ombination me hanisms in statisti al [20 ℄ and kineti models [23 ℄) regenerating

nal-state quarkonium yields, parti ularly for harmonium (marginal for bottomonium). Some

predi tions for the LHC even foresee a quarkonium enhan ement insteadof a suppression

[24 ℄.

Inwhatfollows,weshalldis usssomespe i examplesoftheALICEpotentialforthe

rst measurementsof open and hiddenheavyavour produ tion at theLHC[6 ℄.

2. ALICE SUBSYSTEMS FOR HEAVYFLAVOUR MEASUREMENTS

ALICEisageneral-purposeexperiment equipped withdete tors apable of measuring

andidentifyinghadrons,leptons,andphotonsa rossalargerangeoftransversemomentum

from around

100 MeV/c

to about

100 GeV/c

[25 ℄. TheALICE design hasbeen optimised to opewiththe verydemanding environment of high-multipli ity entral Pb-Pb ollisions

at LHC energies, where up to

8000

harged parti les per rapidity unit at mid-rapidity have been predi ted. The studies presented hereafter have been arried out assuming a

onservative harged parti le rapiditydensity of

dN

ch

/dy = 6000

(note thatRHIC results tendtofavourmultipli ityvaluesstilllowerbyaboutafa tor2.5[26 ℄). TheALICEdete tor,

presentedonFig. 1,hasgooda eptan e forheavy avour dete tion. Heavyavour de ay

produ ts are re onstru ted inthe entral barrel (

|η| < 0.9

) omplemented by the forward muon spe trometer (

−4 < η < −2.5

). The ALICE entral dete tors are embedded in a large magnet (L3)providinga weak solenoidal eld(

< 0.5 T

).

IntheALICE entral barrel, harm and beautyparti les aresele ted out of thelarge

ba kground, takingadvantage of their long lifetime 1

. Consequently,the ALICE dete tion

strategy relies onresolving se ondarydeta hed verti es onsisting ofidentied tra kswith

large impa tparameters (

d

0

),the impa tparameterbeingthedistan eof losestapproa h ofaparti letraje torytotheprimary vertex. Pre ision onse ondaryvertexdetermination

isprovided bythe two innermost layersof the innertra king system(ITS)made of sili on

pixeldete tors(SPD).Aresolution

σ

d

0

(rϕ) < 60 µm

isa hieved for

p

t

&

1 GeV/c

. Parti le tra kingreliesonthesix on entri layersofhigh-resolutionsili ondete torsoftheITS:the

twoSPDlayersquotedabove,plustwolayersofsili ondriftdete tor(SDD),andtwolayers

of sili on stripdete tor (SSD),a large volume (

∼ 95 m

3

) time-proje tion hamber (TPC),

1

D

0

mesons haveproperde ay length

cτ

= (123.0 ± 0.4) µm

,

D

±

Figure 1:LayoutoftheALICEdete tor.

and a high-granularity transition-radiation dete tor (TRD) 2

.Parti le identi ation inthe

entral regionis performedoverthe fullazimuth bya

dE/dx

measurement inthetra king dete tors, a large area high-resolution array of TOF ounters, and transition radiation in

the TRD. A spe trometer dedi ated to muon dete tion and identi ation omplete the

ALICEset-up. TheALICEmuonspe trometer onsistsofapassivefrontabsorberoftotal

thi kness orresponding to ten intera tion lengths to absorb hadrons and photons from

the intera tion vertex, a high-granularity tra king system of ten planes of athode pad

hambers, a large dipole magnet reating a eld of 0.7T (eld integral of

3 T · m

), and a trigger systemmade of four planes of resistive plate hambers performing thesele tion of

hightransverse momentum muons. Muonspenetrating thewholespe trometerlength are

measuredwith amomentum resolution ofabout

1 ÷ 2

%[28 ℄.

3. CHARM PRODUCTION MEASUREMENT VIA HADRONIC

DECAYS

ALICE apability for measuring dire t harm produ tion through the re onstru tion

of the ex lusive hadroni de ays have been evaluated using the ben hmark

D

0

_{→ K}

+

_π

−

(and harge onjugate) two-bodyde aymodeof bran hingratio

(3.83 ± 0.09) %

[6,29 ,30℄. Su hameasurement opensthe possibilityofseparating harm frombeautyand providesa

dire twaytoa ess harmtransversemomentumspe trumwhi hisof ru ialinterestwhen

tryingtoassesstheee tsindu edbythenu lear mediuminp-PbandPb-Pb ollisions. A

D

0

andidate onsistsof a pair of oppositely harged tra ks originating from a se ondary

2

π

pointing angle

θ

_pointing

secondary vertex

primary vertex

D reconstructed momentum

0

D flight line

0

d

d

0

0

K

K

π

impact parameters ~100 m

µ

Invariant Mass [GeV]

1.78 1.8 1.82 1.84 1.86 1.88 1.9 1.92 1.94 1.96

Events/ 2 MeV

0

2000

4000

6000

8000

10000

12000

Invariant Mass [GeV]

1.78 1.8 1.82 1.84 1.86 1.88 1.9 1.92 1.94 1.96

Events/ 2 MeV

-200

0

200

400

600

800

1000

1200

1400

Figure2: Sket hof the

D

0

→ K

+

_π

₋

de ay(lefthandpanel).

K

+

_π

₋

invariant-massdistribution

orresponding to

10

7

entral Pb-Pb events (right hand panel) after sele tion uts applied; the

ba kground-subtra teddistributionisshownin theinsert.

vertex ( f. Fig. 2 left hand panel) whi h has a

K

+

_π

−

mass in the range

M

D

0

± 3 σ

i.e.

|∆M| < 12 MeV/c

2

inthepresentstudy ( f. Fig.2right handpanel).

Extra ting a

D

0

signal with a good signi an e in entral Pb-Pb ollisions requires a

drasti sele tion pro edure to redu ethe huge ombinatorial ba kground by at least

6 ÷ 7

orders of magnitude (

S/B ∼ 10

−6

in themassrange

M

D

0

± 3 σ

beforeanygeometri al or kinemati al sele tion). A dedi ated set of uts (distan e of losest approa h between the

tra ks,

K

and

π

minimumtransversemomentum,andde ayangle)detailedinRef.[29 ,30℄, improves the

S/B

byabout two orders of magnitude. The

S/B

ratio isthen in reased by threeadditionalordersofmagnitudeimposinga ombined utonthevaluesof

d

K

0

× d

π

0

and

cos θ

pointing

3 (

d

K

0

×d

π

0

< −40, 000 µm

2

and

cos θ

pointing

> 0.98

inthissimulationstudy). Cut tuninghasbeenperformedinthepresentstudyforea hseparate

D

0

transversemomentum

bin. With

10

7

Pb-Pb events,weexpe ta

p

t

-integratedsigni an e of

37

andlargerthan 10 up to

p

t

∼ 10 GeV/c

. The lower

p

t

limit is expe ted to be about

1 GeV/c

and even lower inp-p ollisions ( f. Fig.3).

4. BEAUTY MEASUREMENTS FROM SEMILEPTONIC DECAYS

4.1 Single in lusive produ tion ross-se tion measurement using muons

Beauty produ tion in Pb-Pb ollisions will be measured in ALICE via semi-muoni

and semi-ele troni de ays in the pseudo-rapidity regions

−4 < η < −2.5

and

|η| < 0.9

respe tively [28 ℄. In the semi-muoni de ay hannel, both in lusive muons and

opposite-signdimuonsare onsidered. Thedimuonsample isdividedinto two topologi allydistin t

ontributions:

b

- hainde ays(named

BD

same

inFig.4(d))oflowmass

M

µ

+

_µ

−

< 5 GeV/c

2

and high transverse momentum ( f. Fig. 4(a)) and muon pairs where the two muons

originate fromdierent quarks (

BB

diff

)emitted at largeangles resulting inlarge invariant 3

θ

pointing

isdenedastheanglebetweenthe

D

0

andidatemomentumandthelinejoiningtheprimary

[GeV/c]

t

p

0

2

4

6

8 10 12 14 16 18 20

dy [mb/(GeV/c)]

_t

/dp

NN

0

D

σ

2

d

-5

10

-4

10

-3

10

-2

10

-1

10

1

10

50)

×

= 14 TeV (

s

pp,

5)

×

= 8.8 TeV (

NN

s

p-Pb m.b.,

= 5.5 TeV

NN

s

Pb-Pb 5%,

+

π

K

→

0

D

Figure 3:

p

t

-dierential ross-se tion per nu leon-nu leon ollision for

D

0

produ tion as

ex-pe tedtobemeasuredwith

10

7

entralPb-Pbevents,

10

8

minimum-biasp-Pbevents,and

10

9

p-p

minimum-bias events. Statisti al (inner bars) and quadrati sum of statisti al and

p

t

-dependent systemati errors(outerbars) areshown. An overallnormalisationerrorof9% forPb-Pb, 9%for

p-Pband5%forp-pisnotshown.

masses

M

µ

+

_µ

−

> 5 GeV/c

2

( f. Fig.4(b)). The beautysignal isenhan ed withrespe tto other sour es ( harm and

π

/

K

de ay-in-ight) applying a low

p

t

ut-o set to

1.5 GeV/c

in this study. Using Monte Carlo predi ted line shapes for

c¯

c

,

b¯b

, and de ay ba kground, ts are arried out to nd the

b¯b

fra tion in the three dierent data sets aspresented in Fig.4(a), (b), and ( ). Rawmuon yields arethen onverted into in lusive

b

-hadron ross-se tionfollowingthemethodinitiallydevelopedfortheUA1experiment[30 ℄. Theexpe ted

performan e forthe measurementof

b

-hadron ross-se tionfor

10

7

entral Pb-Pb ollisions

is plotted inFig. 4(d).

b

-de aymuon statisti s islarge over thewhole

p

t

range allowing a tight mapping of theprodu tion ross-se tionupto

p

t

∼ 20 GeV/c

.

4.2 Single in lusive produ tion ross-se tion measurement using ele trons

Ele trons from semileptoni de ay of

b

quarks are hara terised by a hard transverse momentumspe trum anda largeaverage impa tparameter (typi ally ofa fewhundred of

mi rons) withrespe tto other ele tronsour es: pions misidentied as ele trons,de ays of

primary prompt harmed hadrons, de ays of light mesons (e.g.

π

0

, Dalitz,

ρ

,

ω

,

K

), and photon onversions in the beam pipe or in the ITS inner layers ( f Fig. 5). The ALICE

dete tionstrategy will thenrelyon thesele tion ofdispla edtra ksidentiedasele trons.

Ele tronidenti ation isperformed ombininginformation fromTRDandTPC.For a

TRDele tronidenti atione ien yof

≃ 90 %

,a1%pion ontaminationisexpe ted. This e ien yisexpe tedtoberoughly onstantinthemomentumrange ontaining thelargest

[GeV/c]

[GeV/c]

t

min

p

t

B p

1

0

5

10

15

20

₁₀

]

−1

[GeV

_t

dN/dp

[GeV/c]

10

min

3

t

B p

1

10

10

) [mb]

5

min

t

p

≥

B

t

(p

NN

B

σ

−5

10

10

7

−4

10

10

−3

9

10

−2

10

−1

10

_{Single muons}

same

BD

diff

BB

−1

dN/dM [GeV

]

1

2

3

4

5

0

10000

15000

20000

all processes

open charm

open beauty

a)

5

8

11

14

17

20

10

−1

1

10

10

2

10

3

10

4

all processes

open charm

open beauty

b)

all processes

open charm

open beauty

decay

5000

Mass [GeV]

d)

c)

Mass [GeV]

dN/dM [GeV

]

−1

Figure 4: Ba kground subtra ted invariant mass distributions of

µ

+

_µ

₋

pairs produ ed in

10

7

entral Pb-Pb ollisions in the low (a) and high mass regions (b). A

p

t

> 1.5 GeV/c

ut-o has been applied to muon tra ks. Charm and beauty signals are plotted in dashed and dotted line

respe tively. ( ) Single muon transverse momentum distribution. (d) Expe ted performan e for

themeasurementof thein lusive

b

-hadron ross-se tionin

−4 < y

B

< −2.5

asafun tionof

p

min

t

. PYTHIApredi tions(solidline)usedto produ ethesignalarealsoshown.

[GeV/c]

t

p

2

4

6

8

10

12

14

16

18

20

[a.u.]

t

dN/dp

-6

10

-5

10

-4

10

-3

10

-2

10

-1

10

1

e from b

e from c

other e

pion

m]

µ

[

0

d

-1000

-500

0

500

1000

[a.u.]

₀

dN/d d

-4

10

-3

10

-2

10

-1

10

e from b

e from c

other e

pion

> 1 GeV/c

t

p

Figure 5: Comparisonofele trontransversemomentum (lefthandpanel)andimpa tparameter

proje tioninthetransverseplane(righthandpanel)frombeauty, harm,lightmeson, onversion,

m]

µ

[

min

|

0

|d

0

50

100 150 200 250 300 350 400

Signal purity, S/(S+B)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

m]

µ

[

min

|

0

|d

0

50

100 150 200 250 300 350 400

central Pb-Pb events

7

Signal in 10

5

10

6

10

7

10

> 1 GeV/c

t

p

> 2 GeV/c

t

p

> 3 GeV/c

t

p

Figure6: Expe tedsignalpurity(lefthandpanel)andsignal(righthandpanel)ofre onstru ted

beautyde ayele tronsasafun tionoftheimpa tparameterthresholdforthreedierentvaluesof

transversemomentum ut-oin

10

7

entral Pb-Pbevents.

and ele tron-tagging probability for ele trons is expe ted to be

≃ 90 %

while ele tron-tagging probability for pions is expe ted to be at the level of 1% up to

p ∼ 2 ÷ 3 GeV/c

(in reasing as a fun tion of

p

to ex eed 60% for

p ∼ 15 GeV/c

). TRD-TPC ele tron identi ationisthereforeexpe tedtoredu espion ontamination by

4

ordersofmagnitude. Theexpe tedbeautysignalpurityand statisti sasafun tionoftheimpa tparameter

ut-ofor dierent values ofthe

p

t

thresholdareshowninFig.6 leftandrighthand panel respe tively [32 ℄. For instan e,

p

t

> 2 GeV/c

and

200 < |d

0

| < 600 µm

are expe ted to provide,for

10

7

entral Pb-Pb ollisions,an ele tronsampleof

8 × 10

4

witha90%purity.

An upper limit on

d

0

is applied here in order to redu e long lived strange parti les and tra ks suering fromlarge angles atterings indete tormaterials.

Finally, the

b

-de ay ele tron transverse momentum distribution is obtained after sub-tra tion of the remaining ba kground ( f. Fig. 7 left hand panel). We intendto subtra t

the remaining ba kground from harm using the hadroni harm produ tion ross-se tion

measurement (des ribed earlier) while the steeply falling (< 2%for

p

t

&

4 GeV/c

) de ay ba kground(frompionstaggedasele tronsandothersour es)willbeestimatedwithMonte

Carlo simulations fromthe measured harged pion pt distributions. The orresponding

b

-hadron ross-se tionperunitofrapidityasafun tionoftheminimumtransversemomentum

(

p

min

t

) is inferred à la UA1 just like for the muon hannel as des ribed in the previous se tionandthe expe tedperforman e showninFig.7 (right handpanel).

b

-quark quen h-ing ee ts on the

b

-hadron ross-se tion are also represented inFig. 7 (right hand panel) but only witha view of illustration sin e any suppression pattern will be assessed from a

omparison with the referen e ross-se tion provided by p-p data. Good performan e for

semi-ele troni beautydete tionarealsoexpe tedinp-p ollisionsbutnot overedinthese

pro eedings, for detailson p-p studiesseeRef. [33 ℄.

5. QUARKONIUM PRODUCTION MEASUREMENTS

[GeV/c]

t

electron p

0

2

4

6

8 10 12 14 16 18 20

dy [mb/(GeV/c)]

t

/dp

e

NN

σ

2

d

-7

10

-6

10

-5

10

-4

10

-3

10

-2

10

= 5.5 TeV

NN

s

Pb-Pb,

e

→

c

→

e or b

→

e from b

[GeV/c]

min

t

B p

0

5

10

15

20

25

30

) [mb]

min

t

> p

_t

/dy (p

B NN

σ

d

-6

10

-5

10

-4

10

-3

10

-2

10

= 5.5 TeV

NN

s

Pb-Pb, 0-5%,

semi-electronic decay channel

/fm

2

= 25--100 GeV

q

= 0

b

m

= 4.8 GeV

b

m

Figure7: Expe tedperforman eforthemeasurementofthe

p

t

-dierential

b

-de ayele tron ross-se tion per nu leon-nu leon ollision as a fun tion of transverse momentum for

10

7

entral

Pb-Pb ollisions (left hand panel). Statisti al (inner bars) and systemati (outer bars) errors are

displayed. Correspondingin lusive

b

-hadron ross-se tionasafun tionof

p

min

t

(righthandpanel). An overall normalisation error (9%) is notin luded. Quen hing predi tions from al ulation [9℄

are superimposed for a massiveand massless

b

quark and a transport oe ient

q

ˆ

in the range

25 ÷ 100 GeV

2

/c

.

in the entral barrel and forward muon spe trometer respe tively. Des ription of key

de-te tors involved inquarkonium dete tion and their expe ted performan e are summarised

inTab. 2. Combined measurementsat entral and forward rapiditieswill allowto probe a

ontinuousrange ofBjorken-

x

withvalues aslowas

10

−5

shedding morelight onthes ale

dependen eof partondensitiesinthesmall-

x

regime.

Expe ted invariant mass resolution (quoted in Tab. 2) allow to resolve the omplete

quarkonium spe trum (J/

ψ

,

ψ

′

,

Υ

,

Υ

′

,

Υ

′′

). Resonan e signals are extra ted integrating

invariant mass spe tra around the resonan e mass, mass windows are xed to

±2 σ

and

±1.5 σ

for dimuon and diele tron de ay hannels respe tively in these simulation studies ( f. Fig 8 andFig 9).

Expe tedquarkoniumsignal,ba kground,signal-to-ba kground,andsignalsigni an e

with

500 µb

−1

ofintegratedluminosity(oneyeardatataking)and for entral ollisionsare

presentedinTab.3andTab.4indimuonanddiele tron 4

hannelsrespe tively. For

harmo-niumstates,despitelargeexpe tedsignalsamples(

∼ 130, 000 J

/

ψ → µ

+

_µ

−

and

∼ 120, 000

J

/

ψ → e

+

_e

−

),expe ted

S/B

ratiosarerelatively smallbuttheexpe tedsignalsigni an e ishighthankstothelargestatisti savailable. Forthe

Υ

,theexpe tedsignalisroughlytwo orderofmagnitudelowerthanthe J/

ψ

onebut at thesame time,inthishigh-massregion, theba kground is lower byaround three orders of magnitude, resulting in asignal

signi- an e of

∼ 30

for a one year datataking period. For ex ited

Υ

,

Υ(2S, 3S)

,even ifsignal statisti s aretight, good performan e arestill expe ted. The expe ted available statisti s

4

avour and quarkonia at ALICE Ra hid Guernane

Table 2: Synopsis of quarkoniumdete tion in ALICE. A eptan e overage: rapidity (

y

) rangeand integrated absolute (normalisedto the full phasespa e)value(

A

),Bjorken-

x

rea h, expe tedglobale ien ies (

ε

), anddileptoninvariantmassresolution(

σ

M

ℓ+ ℓ−

)are quotedforp-pand

Pb-Pb ollisions.

State y range x range

A

/ ndf

2

χ

13.54 / 23

LWidth

0.008234

±

0.001379

GSigma

0.06662

±

0.00140

M1

3.133

±

0.001

Area1

6716

±

100.4

M2

3.727

±

0.016

Area2

189.1

±

32.3

Cbkg

3.112e+04

±

1938

)

2

(GeV/c

µ

µ

M

2

2.5

3

3.5

4

4.5

5

Entries/50 MeV/10^6 s

0

5

10

15

20

25

30

35

3

10

×

_χ

2

/ ndf

13.54 / 23

LWidth

0.008234

±

0.001379

GSigma

0.06662

±

0.00140

M1

3.133

±

0.001

Area1

6716

±

100.4

M2

3.727

±

0.016

Area2

189.1

±

32.3

Cbkg

3.112e+04

±

1938

/ ndf

2

χ

9.571 / 43

LWidth

0.03015

±

0.00953

GSigma

0.09726

±

0.01149

M1

9.529

±

0.006

Area1

67.32

±

3.98

M2

10.09

±

0.02

Area2

18.64

±

2.18

M3

10.43

±

0.03

Area3

10.2

±

1.9

Cbkg

1872

±

274.2

)

2

(GeV/c

µ

µ

M

8

8.5

9

9.5

10

10.5

11 11.5

0

20

40

60

80

100

120

140

160

180

200

220

240

_χ

2

/ ndf

9.571 / 43

LWidth

0.03015

±

0.00953

GSigma

0.09726

±

0.01149

M1

9.529

±

0.006

Area1

67.32

±

3.98

M2

10.09

±

0.02

Area2

18.64

±

2.18

M3

10.43

±

0.03

Area3

10.2

±

1.9

Cbkg

1872

±

274.2

Figure 8: Fitsofthe opposite-signdimuonmass yieldsbothin theJ/

ψ

(leftpanel) and

Υ

mass regions orrespondingtoanintegratedPb-Pbluminosityof

500 µb

−1

andforthe4.4%most entral

ollisions. QuarkoniumsignalisttedwithLandau onvolutedGaussianfun tions(solidlines). No

suppressionorenhan ementhasbeenassumed.

Invariant Mass [GeV]

2.6

2.8

3

3.2

3.4

3.6

3.8

4

)

2

Entries/(Events*GeV/c

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

-3

10

×

Ψ

J/

‘

Ψ

Invariant Mass [GeV]

8.6

8.8

9

9.2

9.4

9.6

9.8

10

10.2

10.4

)

2

Entries/(Events*GeV/c

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

-6

10

×

Figure 9: Combinatorial ba kground subtra ted opposite-sign diele tron invariant-mass

distri-bution (symbols) in theJ/

ψ

mass region (left panel)and in the

Υ

massregion (rightpanel) for

7.5 ×10

7

entralPb-Pb ollisions.QuarkoniumsignalisttedwithGaussianfun tions(solidlines).

Filledhistogramsa ountfortheexpe tedsignalyields. Nosuppressionorenhan ementhasbeen

assumed.

after one year of data taking, should enable enable us to study entrality dependen e of

hidden-to-open heavy avour ratios (J/

ψ

and

Υ

to oppositesign muon pairs frombeauty de ays)and

p

t

dependen eofquarkoniumprodu tionneededto onstrainQGPmodelsand suppressions enarios [6℄.

6. SUMMARY

Withits ex ellent tra king, vertexing, and parti le identi ation apabilities, ALICE

haspromising perspe tives foropen and hiddenheavyavour measurements withabilities

to: fully re onstru t hadroni harm de ay topologies and address (semi)leptoni heavy

Table 3: Charmoniumand bottomoniumstates expe ted signal(

S

), ba kground(

B

), signal-to-ba kground(

S/B

), and signalsigni an e(

S/

√

S + B

)in the dimuon invariantmass range

±2 σ

aroundtheresonan epeakforthe4.4%most entralPb-Pb ollisionandanintegratedluminosity

of

500 µb

−1

[6℄. Chargedparti lerapiditydensityis

dN

ch

/dy = 6000

atmid-rapidity.

State

S (×10

3

₎

_{B (×10}

3

₎

_S/B

_S/

√

_{S + B}

J/

ψ

130 680 0.20 150

ψ

′

3.7 300 0.01 6.7

Υ

1.3 0.8 1.7 29

Υ

′

0.35 0.54 0.65 12

Υ

′′

0.20 0.42 0.48 8.1

Table 4: Charmoniumand bottomoniumstates expe ted signal(

S

), ba kground(

B

), signal-to-ba kground(

S/B

),andsignalsigni an e(

S/

√

S + B

)inthediele troninvariantmassrange

±1.5 σ

aroundtheresonan epeakforthe10%most entralPb-Pb ollisionandanintegratedluminosity

of

500 µb

−1

[6℄. Chargedparti lerapiditydensityis

dN

ch

/dy = 3000

atmid-rapidity.

State

S (×10

3

₎

_{B (×10}

3

₎

_S/B

_S/

√

_{S + B}

J/

ψ

121.1 88.2 1.4 265

Υ

1.3 0.8 1.6 28

Υ

′

0.46 0.8 0.6 13

thesepro eedingswillbesupplementedbymeasuringotherobservablessu hdilepton

orre-lations, se ondaryJ/

ψ

from

b

de ay,J/

ψ

polarisation, and

b

-tagged jets... Theassessment ofthe performan e ofthese additional physi s hannels is urrently underway.

A knowledgments

PartofthisworkwassupportedbytheEUIntegrated Infrastru tureInitiative

Hadron-Physi s Proje tunder ontra t RII3-CT-2004-506078.

Referen es

[1℄ S. Alekhinet al.,[arXiv:hep-ph/0601012℄,[arXiv:hep-ph/0601013℄.

[2℄ M.Bedjidian etal.,CERNYellowReportCERN-2004-009,[arXiv:hep-ph/0311048℄.

[3℄ P.Nason,S.Dawson,andR.K.Ellis,Nu l.Phys.B303(1988)607.

[4℄ M.L. Mangano,P.Nason,andG.Ridol,Nu l.Phys.B373(1992)295.

[5℄ N. CarrerandA. Dainese,[arXiv:hep-ph/0311225℄.

[6℄ ALICE:Physi sPerforman eReport,VolumeII,ALICECollaboration: FCarminatiet al.

2006J.Phys.G:Nu l.Part.Phys.321295-2040.

[7℄ K.J.Eskola,V.J.KolhinenandC.A. Salgado,Eur. Phys.J.C.9(1999)61.

[9℄ M.Djordjevi ,M.Gyulassy,andS.Wi ks,Phys.Rev.Lett.94(2005)112301,

[arXiv:hep-ph/0410372℄.

[10℄ N. Armesto,C.A.SalgadoandU.A.Wiedemann,Phys. Rev.D69(2004)114003,

[arXiv:hep-ph/0312106℄.

[11℄ N. Armestoetal.,Phys.Rev.D71(2005)054027,[arXiv:hep-ph/0501225℄.

[12℄ A. Dainese,Eur. Phys.J.C33(2004)495-503.

[13℄ Zi-weiLinandDenesMolnar, Phys.Rev.C68(2003)044901.

[14℄ HirotsuguFujii, Fran oisGelis,andRajuVenugopalan,Nu l. Phys.A780(2006)146-174.

[15℄ MagdalenaDjordjevi [arXiv:nu l-th/07053439℄.

[16℄ T.Matsui andH.Satz,Phys.Lett.B178,416(1986).

[17℄ A. Jakova etal.,Phys.Rev.D 75(2007)014506.

[18℄ M.AsakawaandT.Hatsuda,Phys.Rev.Lett.92(2004)012001.

[19℄ K.Petrovetal.,PoSLAT2005(2006)153.

[20℄ P.Braun-MunzingerandJ.Sta hel,Phys.Lett.B490(2000)196,[arXiv:nu l-th/0007059℄.

[21℄ K.J.Eskola,K.Kajantie,andK.Tuominen,Phys.Lett.B497(2001)39.

[22℄ K.J.Eskolaetal.,Nu l.Phys.A696(2001)715.

[23℄ R. L.Thews,M.S hroedterandJ.Rafelski,Phys.Rev.C63(2001)054905,

[arXiv:hep-ph/0007323℄.

[24℄ A. Androni etal.,[arXiv:nu l-th/0611023℄.

[25℄ ALICE:Physi sPerforman eReport,VolumeI,ALICECollaboration: FCarminatietal.

2004J.Phys.G:Nu l.Part.Phys.301517-1763.

[26℄ K.J.Eskolaetal.,Nu l.Phys.A696(2001)715-728.

[27℄ W.-M. Yaoetal.,J.Phys.G33,1(2006).

[28℄ R. Guernaneetal.,ALICE-INT-2005-018.

[29℄ N. Carrer,A. Dainese,andR.Turrisi,J.Phys.G:Nu l.Part.Phys.29(2003)575-593.

[30℄ A. Dainese,Ph.D. Thesis,[arXiv:nu l-ex/0311004℄.

[31℄ C.Albajaretal.,UA1Collaboration,Phys.Lett.B213(1988)405;C.Albajaretal., UA1

Collaboration,Phys.Lett.B256(1991)121.

[32℄ F.Antinorietal.,ALICE-INT-2005-033.